Telemetric transmitter



Dec. 23, 1952 s. l.. ADELsoN 2,623,112

TELEMETRIC TRANSMITTER Filed Nov. 2o, 195o s sheets-sheet;

Il f5 5?.

1N V EN TOR.

B" JM & U u fl 9 m, 8 w 3 .d O z ilu IIWIIJ. w1 5 f w. f) s. 7 m A I N x w m ,.21 n @T V l.: 1 i a ,.l` n Lm@ M n n FIGURE 5 Dec. 23, 1952 S. L. ADELSON TELEMETRIC TRANSMITTER BY fw Patented Dec. 423, 1952 TELEMETRIC TRANSMITTER Samuel L. Adelson, Tucson, Ariz., assignor to Infilco Incorporated, Tucson, Ariz., a corporation of Delaware Application November 20,1950, Serial No. 196,668

Claims. 1

This invention relates to a telemetering transmitter, in which the duration of a signal telemetered to a remote location bears a desired relation to the magnitude of a measurable physical condition, such as the rate of flow of a fluid in a conduit, the elevation of the surface of a liquid in a tank or basin, and the like.

The art of telemetering signals of a time duration bearing a desired relation to the magnitude of a physical condition is not new. However, in my improved telemetering transmitter I employ new means for sensing such physical condition by which friction is entirely eliminated and high accuracy of operation obtained.

I utilize the well known fact that oscillations in an electronic oscillating circuit cease when a metallic substance dissipates the energy which sets up the oscillations, to provide an exact means for sensing the magnitude of the condition to be measured. For example, when it is desired to measure the distance from a datum level to the actual liquid level in the high pressure leg of a manometer to obtain telemetering signals proportional to a ow, the metallic substance which acts to stop oscillations in the oscillating electronic circuit can be any member which is moved in response to changes in the liquid level in the high pressure leg of a manometer. In the preferred embodiment of the invention I utilize the manometric liquid itself as the metallic substance and move the means which set up oscillations in the electronic circuit from a datum level along the high pressure leg of the manometer.

It is an object of this invention to provide a telemetering transmitter of the general type referred to employing new and improved means for sensing the physical condition to be metered.

Another object of the invention is to provide a telemetering transmitter which is capable of accurately determining the location of the mercury level in ya manometer Without the use of floats and friction creating means such as stuffing boxes, the term mercury being used herein to designate any electrically conductive manometric liquid.

Another object of the invention is to provide a telemetering transmitter which transmits a signal of a length directly proportional to the ow of a iluid through a conduit.

Another object is to provide a telemetering transmitter operating on a time cycle which is capable of telemetering signals of the proper duration during approximately 90 per cent of each cycle.

Other objects of the invention will become, apparent upon consideration of the followingdetailed description and of the claims.

The invention is particularly useful in telemetering signals corresponding to a flow rate through a conduit and will, therefore, be described as applied thereto. However, `the invention is not limited to this particular application, but may be used in telemetering signals correspending to any variable condition which can be translated into a pressure differential.y

In the present art of telemetering signals corresponding to allow through a conduit, the differential pressure across the upstream and throat sections of a Venturi tube, or across the sections upstream and downstream of an orifice in a conduit produced by a fluid ow therethrough, is usually communicated to a manometer containing a manometric fluid, such as mercury. In one leg of the manometer rides a float which rises and falls with the mercury level as the flow through the conduit varies, the level of the mercury at any time depending upon the flow rate through the conduit at that time. The vertical movement of the float is translated into a rotary movement of a shaft which extends from within the manometer leg through a stuffing box to atmosphere. As the manometer leg is 'usually under pressure the stuiiing box must be pulled up tightly to prevent leakage, and this conduces to friction, which in turn aiects the accuracy of the device. Furthermore, the system of mechanical linkages used to translate the vertical movement of the float to a rotary movement of the shaft includes friction causing elements which also aiiect the accuracy of the device.

My improved telemetering transmitter also utilizes a manometer, the mercury level in one leg of the manometer at any time depending upon the rate of flow through the conduit, the duration of the transmitted signal being a function of the distance of this level from a zero or datum level. However, in my apparatus the position of the mercury at any time is accurately determined without the use of a iloat, shaft, stuiiing box and linkages associated with the oat and shaft. Instead of the usual friction creating means I use as a detector of the location of the mercury level an electronic oscillating circuit.

The invention will be more readily understood from a consideration of the accompanying drawings, wherein like reference characters designate similar elements and wherein:

Figure 1 is a front elevation of a preferredembodiment of the invention showing the means 3 for detecting the mercury level oi the manometer in zero level position;

Figure 2 is a partial front elevation of the apparatus of Figure l showing the means for detecting the mercury level of the :nanometer in their lowermost position;

Figure 3 is a vertical sectional view along line 3-3 offFigure `1 showing also the connections to the Venturi tube;

Figure 4 is a cross sectional View along line 4--4 of Figure 2;

Figure 5 is a wiring diagram; and

Figure 6 is an alternate wiring diagram.

Referring rst to Figure 3, a'Venturi'tube VIii is in a conduit I I, through which a'fluid flows. "The upstream section l2 of Venturi tube IIJ communicates by means of a conduitIS .withzleglldloi a manometer I5, while the throat I6 of .Venturitube I0 communicates by means of a conduit"I'Iwith the other leg I8 of manometer I5. The upper l-fen'd ffmanometer `leg I Iii has anV `enlarged section I9.' v"IhelegIllito which thelupstreamisection I 2 communicatesvby/-meansoi conduitIS is `=frr1ade of an electrically noneconductive substance fsuch -as `plastic and `has internal and `external sections rectangular in -iorm nl'-Ifhemanometer I5 contains a metallic manlometric'sliquid rsuch asmercury M. `When there vlis'no fow through' the Venturi tube, the mercury `levels inflegs I4 and I 8' willbe the same, this level beingV thezero orbasi'c level Z.

`-A`s bestshown in Figure l, a lever 2Q has near lione-tenda' bearingfz If and-is adapted' toi osclllate abo'ut astationary vpin2i2. A counterweight 23 Vat theend of lever"20-nearly, but not completely, 'f--balances the leverand its'associated parts. The -fiotheror inner endof lever 20 isbifurcated and ff'at 'thelend of each branch is fixed a coil 24, these #coils vbeing part ofan electronic oscillating circuit. The c'oilsfzv are so mounted that they stradle the mercuryr column in leg I4 of manometer 54 as the--leverIZD oscillates about pin 22. Inter- .'medi'ate'the ends 'of lever'Z `is nxeda stationary H'stub shaft 25 von-which a roller'26 may rotate.

fAsynchronous motori 30 provided with` a reff'lduction'gear; not' shown, has anv output'shaft 3|. fOri`thisshaft 'which rotates at` a relatively slow '.'lspe'edis'xed a cam 32, which rotates at a uni- Tform speed in4 counterclockwise direction. The `frollerfZE.rides on the contoured edge of cam 32 .Sand is.heldiinlcontactv with itby gravity. The "1 dimensions and contour of the cam 32 are such that-'ther upperf limit -of movement yof the coils l'i24eis'slightly higherthanthe Zerolevel Z' of the fmercury' M, while the lowe'rlimit of movement oi.`

the coils 24 issomewhatlower' than the lowerfmost level-the' mercury in leg-I4 can reach, this jlevel :corresponding'fto the maximum flow rate ithrough conduit' I I.

The differential pressure produced by a Venturi "tubeor orifice varies Las the square of the flow tirate; :therefore .the distance from the zero level 'IFZ in leg `Hly 'of'.manometer I5 to the mercury `level .ifatscanytime will` also vary as the square of the fiow rate. However, by providing .thecam 32 with ,inthe-propercontour; the time required forfthe coils 11124;.:to lower between vthe zero level' Z andthe level :ofithefmercury in leg Mrnay be madeA directly c proportional to the flow rate through conduit II f 'corresponding to the level of the'mercury.

""It is during this `time that the signal is tele- 4metered to the remote location.

It has beenvfoundentirely'satisfactory in many .f1cases:tolftelemetercthese'signals 'once every 'min- :rute: the duration ofzasignalz3in any :minute de-"1 `meansI described later, Iarefprovi'ded whereby during approximately 90 Vper cent`f`the cycle the transmitter is capable of telemetering signals of ""the proper duration and during the remaining 10 nper centof `the cycle the coils 2li are restored to their uppermost position and then lowered to :the lzero level-Zfatfwhich the timing in the cycle ""begins.

"Onthebamrili is fixed an extended arm 33, the

outeraendv Stof: which is adapted to engage the actuating roller 35 of a double throw snap action "switch`-35 (one type of which is known as Micro Switch as manufactured by a division of First "Industriali Corporation'yof.SlFreeport, lllin'oisl at f the moment whenitheii'aeroileveLZ?isreachewby 'tlie coils 124;: whereby 4theilriormallyfopencontact of switch: 3S v.is closed for aishort 'periodiofltime For convenience,'switches of i the type. of "switch but it will beunderstoodthat other switches' of this type :can `be Insed. Closing of thenormally open contact 'of switch 35 energizes'the coil 38 lofthree `poletrelay^39 (see Figure 5) to` start tele- "metering"the signal. A"Relayrlil'is of' theelectrical finterlocir type such that a momentaryI closing fof the switch will keep the relay coil? 38` 'energized and-'maintaintelemetering the signal.

f When the coils 424 reach `the* actual "level lMI of the mercuryiinleg.l IA of manometer I5', the relay fcoilfflxis Ashortcircuit'ed .to dee'energizethe coil @andA telemetering `of the signal -will cease. The j'operation `of af'relay, such.-as39,islwellknown to Vlthose skilled in theI art.

- Also mounted'on thearm53, near its outerend 34, -is afi-xedpinf: about which a roller 4I is free to rotate. Fixed tto -uleverZ D.. intermediate the .-,pins 2I and-25.is-anextensionllz whichlies in the `path of Atravel-ofroller 4 I.

v When' the Vcam 32 has rotated'through an angle :.(approXi-mately'SZW) such that the coils 24 have reached their lowermost position, as shown in Fig- .ure 2;. the roller` 4IA Aon 'arm .33 willv contact the underside .of extension 42 andliit the free end of `l'everZI .and coils 24" to their uppermost `position and then lower the 4lever 2D and coils 24 until the rollerl 2B enlever 20 comes to rest onvcam 32 just before'coils 'reach the zerolevel Z. This movement of thelever'20 by'the'roller III is comfpleted in about-Hiperv cent oftheentire` oper- `ating cycle.

yWhen the coilsi24 reachthezero level, telemetering of the signal begins.

- Fixed tothe cam 32 `is also anl arm 43 having at itsouter end an extension 44 adapted to contact the roller 450i a double throw Micro Switch VMi.

' 3i) has stopped.

The function of larmfill3 andswitch Nilis to give an' alarm, stop motor 3D and stop telemetering signals upon failure of the electronic'circuit to operate. Usually such failure occurs at theexpiration of :the: liie cian electronic tube. .Upon

replacement of this tube by a serviceablesone and momentarily opening a normally closed switch, the system is once again placed in operation.

In the schematic wiring diagram of Figure 5, the electrical circuit used in one mode of operation of the invention is shown.

An electronic oscillating circuit is indicated generally at 58. It is shown for purposes of illustration as of the inductive type and comprises an electronic tube 5| having a plate 52, grid 53, cathode 54 and heater 55. A transformer |80 is shown as supplying power for the heater 55. A rectifier circuit is indicated generally at 56. One Of the coils 24 isin the plate circuit and the other is in the grid circuit of tube 5|. The coils 24 and the inter-electrode capacities of the tube 5| form an oscillating circuit. A relay 51 is connected in the plate circuit of the tube 5I.

As is well known in the art, when coils 24 are properly disposed and free to react one with the other, oscillations are set up and the current in the plate circuit may be made of too low a value to actuate the relay 51. However, if a metallic substance such as the mercury M is interposed between the coils 24, oscillations will cease and the current in the plate circuit will immediately increase to such a value as will energize the coil 58 of relay 51 and bridge terminals 59 and 66 with pole 6| of relay 51. When the mercury M is removed, oscillations will be restored, the current in coil 58 of relay 51 will be reduced to a value where the coil will be de-energized, and the circuit between terminals 59 and 68 of relay 51 will be opened.

I have found that to stop oscillations it is not necessary for the mercury to be completely interposed between coils 24. When the mercury enters the space between the coils only part way, oscillation will cease and the relative position of the surface of the mercury and say, the center of the coil, at which oscillations cease, will always .be the same.

The operation of my telemeteringtransmitter is as follows:

First assume that the ow rate through -the conduit is such that the mercury level in leg |4 is at say M| and in leg I8 at M2: When the coils 24 reach the zero or datum level Z of the mercury, the end 34 of arm 33 will contact roller 35 of Micro Switch 36 (see Figure 1) and actuate the Micro Switch 36 to bridge its terminals 62 and 63 by pole 64 (see Figure 5). Current will then ow from line L| of A. C. .power supply through conductors 65 and 66, terminal 63, pole 64 and terminal 62 of switch 36, line 61, terminal 68, pole 68 and terminal |02 of double throwswitch 18, line 1|, coil 38 of relay 39, resistor 12 of relay 39, normally closed switch 13, conductor 14 and back to line L2 of the power supply. This will energize coil 38 to bridge terminals 15 and 16 by pole 11 of relay 39, unbridge terminals 18 and 19 normally bridged by pole 88 of relay 39, and bridge terminals 8| and 82 by pole 83 of relay 39.

When the end 34 of arm 33 leaves the roller 35.01 switch 36 the contacts 62 and 63 of the switch will be unbridged. Howeveiyrelay coil 38 Will remain energized, current now passing from line L| through conductors 65 and 66 to terminal 15, pole 11, terminal 16, coil 38, resistor 12, switch 13 and conductor 14 to line L2.

While relay coil 38 remains energized, current will now from line Ll through conductor 84, load 85, terminal 82, pole 83, terminal 8|, conductor 86, terminal 89, pole 88 and terminal 81 of Micro 'Switch 46 and conductor 98 to L2. The duration of this ilow of current `constitutes the telemetered signal to the load 85, the latter being in some cases say a motor which is to run only for the duration of the signal to operate say a chemical feeder for the purpose of treating a water supply flowing through the conduit in proportion to the flow rate therethrough.

The cam motor 30 under normal conditions op- Vcrates continuously, its power being derived'from the source of power Ll through conductor 65, normally closed switch 9|, motor 30, terminal 89. pole 88, terminal 81 and conductor 99 yto line L2.

When coils 24 in their downward movement reach the level Mi of the m-ercury in leg I4 of manometer i5, oscillation of the electronic circuit will cease. This energizes the coil 58 of relay 51 to bridge terminals 59 and 68 by pole 6|. This closes a circuit from L'I through. conductors 65 and 66, terminal 15, pole 11, and terminal 16' of relay 38, conductor 1|, terminal |82, pole 69 and terminal 68 of double throw switch 10, conductor 61, terminal 62, pole 64 and terminal 63a of Micro Switch 36, conductor 91, terminal 68, pole 6| and terminal 59 of relay 51, conductor 98, resistor 12, lswitch 13, and conductor 16 to L2. This will short circuit coil 38 of relay 39 to restore the poles of relay 39 to their original position and the signal will stop as the circuit is broken at pole 83 and terminal 82 of relay 39.

During the rotation of cam 32, the end 86 of arm 43 will contact roller 45 of Micro Switch 46 so that terminal 81 will be bridged to terminal 92 by pole 88 during the passage of end 44 along the roller 45. Under normal operation this occurs after relay 39 is de-energized and thus has no eilect upon thel circuit, since the current to operate motor 38 is obtained from line LI, through conductor 65, switch 9|, motor 36, conductor 86, terminal 19, pole 88, terminal 1,8, conductor 93 to line L2.

If, however, due to a failure in the electronic circuit, relay 51 fails to operate, the coil 38 of relay 39 will have remained energized when end 44 oi arm 43 contacts roller 45 of Micro Switch 46. Bridging of contacts 81 and 92 by pole 88 will, under these circumstances, close a circuit from line L| through conductors 65 and 56, terminal 15, pole 11, line 96, lamp or other signal 95, conductor 96, terminal 92, pole 83, terminal 81 and line 98 to L2. At the same time motor 38 will stop, as its circuit is broken both between pol-e and terminal 19 of relay 39 and at pole 83 and terminal 89 of switch 46. At the same time no signal will be telemetered as the circuit is broken between pole 88 and terminal 89 of switch 46. After the failure of the electronic circuit is corrected, such as replacing a defective tube, the switch 13 is momentarily opened to rie-energize the relay 39 and break the circuit through the signal 95 and the coil 38, after which the alarm ceases and normal operation is resumed.

For purposes of establishing the zero level Z of the mercury M in leg i4 of manometerl I5, the single pole normally closed switch 9| is placed in series with the motor 36 and the single pole double throw switch 'd8 is placed in the line 1| leading to the junction of terminal 16 and coil 38 of relay 39.

The procedure to establish the zero level is as follows: Mercury is placed in the manometer i5 until its level is somewhat below its zero level Z. Then by manipulating switch 9|, the cam 32 is rotated until the roller 26 on lever 20 is in line jwith the zero mark indicated jby'thearrowon 75 cam 32 and the end 34 of arm 33 engages roller v3,5 lof Micro Switcb/ wherebycoll 38 of relay 33 `is, lenergized to 'close the relay.` In this position the coils 24 are at the zero level of the mercury. The' pole 63 of ,switch 10 is then placed so that terminal |02 isbridged by pole 69 with terminal Additional mercury is now slowly poured into manometer I 5. When the mercury has risen between the coils 24 to such a level as will cause closingfof relay 51 in the plate circuit of tube 5|, the relay v39 will open since closing of relay 51 shortcircuits coil 33 of relay 33. `It is at the moment when relay 51 closes and relay 33 opens that no further mercury is added and the zero level Z has been established. After this the switch is restore-d to its normal position where pole 69 bridges contactse and |02.

Inthe circuit just described, the telemetering will not be restored after a failure of a tube until 'the defective tube has been' replaced. Where this would be objectionable,y the circuit shown in Figure 6 may be used in which a stand@ by tube is automatically placed in service, so that telemetering is not interrupted. Atthe same time a signal is given to show that the standby tube is now in service and that the defective tube should be replaced by a new tube, such new tube then acting as the standby. Immediate replacement of the defective tube is not necessary as the standby tube will function throughout its life which is of the order of 3000 hours.

In this circuit there are two electronic tubes 5I and 5|a, having plates 52 and 52a, grids 53 and 53a and cathodes 54 and 54a respectively, the plates, grids and cathodes respectively being connected in parallel.

Relay 3S of Figure 5 is replaced by a relay 33a, Micro Switch 46 of Figure 5 is replaced by Micro Switch 46a, a relay |03 is added and a three pole double throw switch |04 with off position is added; arm 43 is removed and Micro Switch 45a is in the path of travel of the end 34 of arm 33.

The other elements shown in Figure 5 are the sameas those of Figure 5.

Cam motor runs continuously, the current being from LI, through conductors |33 and |30, normally closed switch 9|, conductor |3|, motor 30 and conductor |32 to L2.

Assume that the poles |05, |05 and |01 of switch |04 bridge terminals |00 and |03 and ||2 and ||6 and ||3, respectively, and that coil ||1 of relay |03 is (ie-energized so that pole H3 bridges terminals H3 and |20. This applies power to heater of tube 5| as follows: From terminal S| of the secondary of transformer |00 through conductor |2|, terminal |20, pole IIB, terminal H9, conductor |22, terminal ||5, terminal pole |05, terminal |03, conductor |23, heater 55, conductors |24 and |25 to S2 of transformer secondary. No power will be applied to heater 55a vof tube 5 la as the circuit of this heater is broken between pole ||ii and terminal |25 of Vrelay |03.

Tube 5| is now in service and tube Ela acts as the standby.

When the roller 26 coincides with the zero mark on cam 32 (at which time coils 24 are at the zero level Z), end 34 of arm 33 will contact roller 35 of Micro Switch 36 and pole 04 will bridge terminals 62 and 63. The relay coils 38a of relay 39a will now be energized and pole 11a will bridge terminals 15a and 16a, pole 80a will bridge terminals 18a and 10a and pole 83al will bridge terminals 8| a and 82a.

The circuit is as follows:

From line L| through conductors |33, |34 and 8y |35, terminal 63 or Micro Switch 36, pole 64, terminal 62`,"terminal "68'of switch 10; poleGS, terminal |02, conductor |31, coil 38aandc`onductors |38 and |56 of line L2. A circuit will also be established to maintain relay 38a` energized whenthe circuit is broken at pole 64 and terminal 63V of Micro Switch 36, when the end'34 of arm 33 leaves roller 35 of Micro Switch" 36 as follows From line L| through conductors |33, |34 and 36, terminal 15a, pole 11a, terminal 16a,'c0il 38a and conductors |38 and |56 to line L2.

A circuit will also be establishedirom line L| through conductor |39, terminal Bla, pole'03a, terminal 82a, conductor |40, load 85 and ccnlductor |4| to line L2.v The durationof'theflw of current throughV this :circuit l'cor'lstitutes'`"the telemetered signal. i

When coils 24 in their downward movement reach the 'level M|` of the mercury inleg `|4 of manometer" I5, the coil 30a of relay v3$|u"will be short circuited to restore the poles'of`rela`y'331 to their original open position, as outlinedin connection with Figure 5, and telemete'rin'g of the signal will cease.

Under normal operating conditions, the poles of relay 35a will always be in their normal'open position when ycoils 24 begin their upward travel. Therefore, when end 34 of arm 33 contacts roller 45 of Micro Switch 46a to close it, there willbe no effect since the circuit in which 46a' islocated is broken ybetween pole a and terminal 13o of relay 39a.

If, however, due to a failure of tube 5|, the poles of relay 39a do not assume their normally open position but remain in a closed position when switch 46a, is closed, :a circuit will be Ves,- tablished as follows:

From line LI, through conductors |33, |34,

terminal 19a, p01@ una, terminal mi, conjductor |46, closed switch 45a, conductor |41, cpil ||1 of relay |03, conductor |46, terminal |`|0 of switch |04, pole |01, terminal ||3, ycoi'iductors |49 and |50 to line L2.

Coil ||1 will now be energized, pole |42 will bridge terminals |43 and |44 and pole ||8 will bridge terminals |20 and |26.

Relay coil H1 will remain energized even though switch 45a opens after the end 34 of arm 33 leaves roller 45 ofMicro Switch 46a.

The circuit of heater 55 of tube 5| .will be broken between pole ||8 and terminal IIB of relay |03 and a closed circuit will be established to heater` 55a of tube 5|a as follows:

From SI of transformer |00 through conductor |2|, terminal |20, pole ||8 vand terminal"|2,6 of relay |03, conductor |45, terminal ||4 of switch 04, conductor |5I, terminal ||2, pole |03, terminal |00, conductor |52, heater 55a, andc'ofnductors |53 and |25 to terminal S2 of transformer |00.

At the same time a circuit will be establhed from line L| through conductors |33 and |55, terminal |43, pole |42, and terminal |44ofrelay |03, alarm and conductor |56 to L2, to give notice that the tube previously in service should be replaced.

Immediately after the defective tube is replaced, the poles of switchv |04 are thrownin the opposite position so that poles |05, |06,and |01 will bridge terminals |08 and ||4, |09 and I5 and ||0 and ||6 respectively. During thetransition of poles |05, |06 and |01, from their previous position to their new position, the power circuit to the c oil ||1 of relay |03 will be broken be ,l

pole |01 and terminal ||3 to de-energize the coil. The poles of the relay will then assume their normally open position and the alarm 95 will cease since its circuit is broken between pole |42 and terminal |43.

When pole |01 bridges terminals ||0 and ||0 in their new position, the relay coil ||1 will remain de-energized since line L| connects to relay ||1 only when pole 80a is bridging terminals 19a and 18a of relay 33a at the time switch 46a. closes. This condition, as outlined above, can occur only when the electronic tube then in service fails. Also coil I |1 does not connect to line L| through conductor |55 unless relay coil ||1 is first energized through pole 80d of relay 39d and switch 46a to bridge its terminals |43 and |44 by pole |42.

With the poles of relay |03 in their normal position and poles |05, |06 and |01 of switch |04 bridging terminals |08 and ||4, |09 and ||5 and and ||6, respectively, power is supplied to heater 55a of tube 5|d as follows:

From SI of transformer |00, conductor |2|, terminal |20 of relay |03, pole ||8, terminal ||9, conductor |22, terminal ||5, pole |00 and terminal |09 of switch |04, conductor |52, heater 55a and conductors |53 and |25 to S2 of transformer |00. Tube 55a is now in service and the replacement tube for tube is now the standby.

A subsequent failure of tube 5|a will fail to de-energize relay coil 38a of relay 39a so that as described above pole 80d will be in bridging position between terminals 18a and 19a when switch 46a closes. This, as already described, will energize coil ||1 of relay |03 to bridge terminals |20 and |29 by pole ||8. A circuit will now be established to apply power to heater 55 of tube 5| as follows:

From Sl of transformer |00 through conductor |2|, terminal |20, pole ||8 and terminal |20 of relay |03, conductor |45, terminal ||4, pole |05 and terminal |08 of switch |04, conductor |23, heater 55, conductors |24 and |25 to S2. This places the tube 5| in service.

When the coil is energized and pole |42 bridges terminals |43 and |44 of relay |03, the circuit from LI through the signal 95 to L2, described above. is closed, so that the signal will indicate that the standby tube 5| has been taken in service and tube 5 la should be replaced. When the defective tube 5|a has been replaced by a new tube, the poles |05, |06 and |01 are thrown in the opposite or original position to de-energize relay coil ||1 of relay |03 and stopthe alarm.

The description of the operation for placing a standby tube in service as given above applies to any subsequent failure of a tube to function.

It will be seen that I have invented a highly accurate transmitter which eliminates errors due to friction and which operates over a long period of time entirely automatically, manual service being limited to the time when replacement of an electronic tube becomes necessary.

Many changes of the preferred apparatus shown and described could be made without departing from the scope and spirit of my invention. Thus, it will be obvious to those skilled in the art that instead of moving the coils 24, the manometer l5 could be raised and lowered. Accordingly, I do not wish to limit myself to the exact structural details of the preferred embodiment described herein for purposes of illustration but not of limitation.

I claim: Y

1. Apparatus for telemetering signals proportional to the magnitude of a condition compris- 10 ing an electronic circuit including an electronic tube, coil means connected in part in the plate circuit of said tube and in part in the grid circuit of said tube and operable to set up oscillations in said electronic circuit, a metallic substance whose position is a measure of the magnitude of said condition, means effecting a, cyclic relative motion -between said coil means and said substance from one predetermined end position to another, means for closing a signaling circuit at the one end position of said movement, and means for opening said signaling circuit when the relative position of said metallic substance to said coil means is such as to stop oscillations in said electronic circuit.

2. Apparatus for telemetering signals proportional to the magnitude of a condition comprising an electronic circuit including an electronic tube, coil means connected in part in the plate circuit of said tube and in part in the grid circuit of said tube and operable to set up oscillations in said electronic circuit. means for cyclically moving said coil means from one predetermined end position to another, a metallic substance whose position is a measure of the magnitude of said condition, said substance being located within the range of movement of said coil means, means for closing a signaling circuit when said coil means is at said one predetermined end position, and means for opening said signaling circuit when said coil means reaches the location of said metallic substance.

3. In a telemetering transmitter including a manometer, an electrically conductive fluid in said manometer, one ieg of said manometer being adapted to be connected to a source of high pressure and the other leg being adapted to be connected to a Source of low pressure, an electronic circuit including an electronic tube, coil means connected in part in the plate circuit of said tube and in part in the grid circuit of said tube and operable to set up oscillations in said electronic circuit, means for gradually moving said coil means along said one leg from a predetermined datum level to a, predetermined lower level, means operative to start a signal when said coil means reach the datum level, and means operative to stop said signal when oscillations in said electronic circuit cease due to said coil means reaching on the downward travel the fluid surfaceV in said one leg.

4. In a telemetering transmitter a manometer including an electrically conductive manometric fluid Vand adapted to be connected to a source of high pressure with one leg and to a source of low pressure with its other leg, said one leg being of an electrically non-conductive material, an electronic oscillating circuit including two .coils and an electronic tube, one of said' coils being connected inthe plate circuit of said tube, the other of said coils being connected in the grid circuit of said tube, said coils straddling said one leg and being so located with respect to one another as to be mutually inductive to set up oscillations in said electronic circuit, means for gradually moving said coils at a, predetermined rate from an upper datum level downwardly to a predetermined lower level, means operative to start a signal when said coils reach the datum level, and means operative to stop said signal when said coils, o n their downward travel, reach the surface of the fluid in said one leg.

5. In combination with a manometer including an electrically conductive manometric fluid and adapted to be connected to a source of high pressure with one leg and to a source of low pressurewith the other leg, said one leg being of non-metallic material, an electronic oscillating circuit including two coils and an4 electronic tube, one of said coils being connected in the plate circuit of said tube, the other of said coils being connected in the grid circuit of said tube, said coils being so located with respect to one another as to be mutually inductive to set up oscillations in said electronic circuit, means for moving said coils along said one leg from an upper datum level to a predetermined lower level at a predetermined rate, said means including a lever supporting said coils, said lever being free to oscillate around a fixed support, acam, means for rotating said cam at a uniform speed, and a member carried by said lever and adapted to ride lon the edge of said cam, means carried by said cam and operative to close an actuating circuit for a signal when said coilsare at the predetermined datum level, and means for opening said actuating circuit when said coils reachthe surface of manometric fluid in said one leg.

6. The apparatus of claim 5 including also means carried in part by said lever and in part by said cam and operative when said coils reach the predetermined lower level to return -said coils to the predetermined datum level at a higher rate than the rate of downward travel of said coils.

'7. In a telemetering transmitter a manometer including mercury and adapted to be connected to va, source of high lpressure with one leg and to a source of low pressure with its other leg, said one leg being of a non-metallic material, an electronic oscillating circuit including two coils and an electronic tub-e, one of said coils being con-- nected in the plate circuit of said tube, the other of said coils being connected in the grid circuit of said tube, said coils straddling said one leg and being so located with respect to one another as to be mutually inductive to set up oscillations in said electronic circuit, means for gradually moving said coils at a predetermined rate from an upper datum level downwardly to a predetermined lower level, a normally open switch, means for momentarily closing said switchA when said coils reach the datum level, a relay connected in fthe plate circuit of said tube and adapted to be actuated when the coils reach the mercury level in said one leg and oscillations cease in said electronic circuit, and an electric circuit including a second relay for actuating a telemetering signal, said circuit being closed by closing of said switch Iand being opened by closing of said first relay.

8. The apparatus of claim 7 including an alarm,y a circuit through said alarm, and means for closing said circuit upon failure of said first relay to break the actuating circuit for said telemetering sign-al when said tubes reach the mercury level in said one leg.

9. A telemetering transmitter comprising a '12 manometer including an electrically conductive manometric fluid and adapted to be connected Ito a source of high pressure with one leg and to a source of low pressure with the other leg, said one leg being of a non-conductive material, an, electronic oscillating `circuit including two coils and two electronic tubes, said tubes having their plates, grids and cathodes connected in parallel, one of said coils being in the plate circuits of said tubes and the other in the grid circuits of said tubes, 'a power circuit for each of said tubes, means operative to close the power `circuit to. one of said tubes and to simultaneously open` the power circuit to the other of said tubes, means for gradually moving said coils downwardly along l said one leg at a predetermined rate from an upper datum level to a predetermined lower level, a relay connected in the plate circuits of said tubes and adapted to be actuated when said coils, on their downward movement, reach the fluid level in said one leg and oscillations in said electronic circuit cease, an electric circuit for actuating a telemetering signal, means for closing said circuit when said coils reach said datum level, said circuit being opened by closing of said relay, and means operative upon failure of said relay to close when said coils reach the fluid level in said ene leg to open the power circuit to said one tube and simultaneously to close the power circuit to said other tube.

10. In an apparatus for telemetering signals proportional to the magnitude kof a condition, said apparatus including a manometer having two legs adapted to be connected to a source of high pressure and a source of low pressure, respectively, and an electrically conductive fluid in said manometer, an electronic circuit including an electronic tube, coil means connected in part in the plate circuit of said tube and in part in the grid circuit of said tube and operable to set up oscillations in said electronic circuit, means for cyclically moving said coil means from one predetermined level to another predetermined level, said manometric fluid having a surface within the range of movement of said coil means, means operative to close a signaling circuit when said coil means reach said one predetermined level, and means operative to open said signaling cir` cuit when said coil means reach said surface.

SAMUEL L. ADELSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,308,645 Chappell et al Jan. 19, 1943 2,403,890 Johnson July 9, 1946 2,419,487 Dresser s Apr. 22, 1947 

